Third-hand smoke consists of the remnants of tobacco smoke that accumulate in clothing, carpeting, furniture, and other similar materials. According to Yael Dubowski, Ph.D., from the Faculty of Civil and Environmental Engineering at Technion-Israel Institute of Technology, and colleagues, harmful pollutants can form when nicotine from third-hand smoke reacts to the air and indoor surfaces. People are then vulnerable to those pollutants by being close to the affected surfaces, such as when a baby crawls on the carpet, or when someone naps on the couch. Even food can be contaminated and harmful.

Not much is known about third-hand smoke and the health hazards it presents, but according to the 2006 surgeon general's report, there is no risk-free level of exposure to tobacco.

In order to understand more about third-hand smoke, Dubowski and colleagues tested how nicotine reacted to indoor air on various surfaces. They found that the interaction between nicotine and indoor air created toxic pollutants on all the surfaces they tested, including cotton, paper, and cellulose. The authors conclude that their research shows that third-hand smoke is dangerous and poses health risks yet to be discovered.